Quality of life as a construct in health and disability research

Definitional issues that affect the measurement of quality of life (QOL) in health care research are discussed. In reviewing a broad sample of health- and disability-related QOL studies, the authors note several characteristics in which respective approaches to measurement differ: (a) In various measurement tools, QOL has been located either within the insider's (i.e., the person being measured) judgment of the 'goodness' of his or her life or outside this judgment. (b) The insider's and/or outsider's values may hold sway in deciding the elements of life that are relevant to QOL within the measurement process, and in rating the degree of 'goodness' of these life domains. (c) QOL models incorporate domains of items varying in breadth and specificity; and they take either a negative or neutral view of functioning. (d) QOL models vary in their complexity, type of linkage between components, and inclusion (or not) of both the insider's judgment and external predictors of QOL. These distinctions are used by the authors in recommending approaches to QOL measurement suitable for health care research aimed at outcome assessment and description of populations.